Dynamic inter-cell channel sharing

ABSTRACT

A mechanism to share channels between cells dynamically and without simultaneous allocation of the same channel by more than one access point achieved by a method for a dynamic inter-cell channel sharing for a first access point in a radio access network, the first access point being associated with a first cell of a number of cells within the radio access network, the first access point being adapted to connecting at least one first user equipment being situated in the first cell, to a network infrastructure, comprising the steps of: receiving from the at least one first user equipment a report indicating whether a specific channel is used in a second adjacent cell of said number of cells, the report being based on a first information sent from at least one second access point, the information indicating whether a specific channel is used in the second adjacent cell.

TECHNICAL FIELD

The present invention relates generally to a method and arrangement foran access point in a cellular radio access network and a method andarrangement for a user equipment in the cellular radio access network.In particular it relates to dynamic inter-cell channel sharing in theradio access network.

DESCRIPTION OF RELATED ART

During frequency planning, channels are assigned to cells such thatadjacent cells are assigned different channels and the same channel isreused only in cells with k cells distance away (k-reuse described in US2005/0096062). A drawback of the fixed channel partitioning achieved byfrequency planning is that only a fraction of the spectrum is availablein a cell and there is no possibility to make the entire spectrumavailable in one cell even if the channels in adjacent cells aremomentarily unused. Therefore the fixed partitioning of frequenciesresults in under utilization of radio channels in many cases.

A more sophisticated version of the classical frequency partitioningmethod is the use of multiple reuse partitions in the same cell. In thiscase a cell is divided into two regions. In the inner part of the cellthe frequency reuse is one whereas in the outer part (cell borderregion) the reuse is larger than one (k-reuse). Such a method isdescribed in US 2002/0119781 A1, depicting a method to be used inOrthogonal Frequency Division Multiple Access (OFDMA) based systems forthe allocation of carriers to different users. The user equipmentperforms measurements on the available carriers, measuring the signalquality on reference symbole channels, for instance the signal-to-noiseratio (SNR) and traffic load measurements, which they feed back to theirown access points. Then the access point makes the scheduling decisionand assigns carriers to the users. However, this scheme is primarily fordownlink, and it does not address the issue of any cooperative behaviourbetween access points in order to avoid the simultaneous allocation ofthe same carrier. Another disadvantage is that it assumes a k-reusesystem with fixed allocation of channels to cells. The main advantage ofthis approach is that on the one hand channels are more efficientlyutilized and on the other hand the interference in the cell border isminimized. However, the allocation of channels to cells is still fixed.

If more dynamic allocation of channels is required there are a varietyof Dynamic Channel Allocation (DCA) schemes available in prior art.Common to these schemes is that they allocate channels to user equipmentcommunications dynamically, depending on e.g. the traffic demands on theavailable channels, on the channel quality, etc. The DCA schemes varydepending on the time dynamics of channel allocation, the distributed orcentralized nature of the scheme, the parameters and measurementinformation used as input for the decision, etc.

Such a DCA scheme is depicted in US2005/0058097 using an orthogonalfrequency division multiple access network, which is to be used forassigning sub-channels in an OFDMA based systems to users in differentcells. In this method, a central controller entity is assumed, e.g., aRadio Network Controller (RNC), which assigns the channels such that noconflict occurs between cells. The problem with this solution is that itrequires a central entity, the RNC that coordinates the allocation,which means higher complexity.

SUMMARY

It is therefore an object of the present invention to provide amechanism to share channels between cells dynamically, withoutsimultaneous allocation of the same channel by more than one accesspoint and without requiring a central entity that coordinates theallocation.

In accordance with the present invention, the object is achieved by amethod for a dynamic inter-cell channel sharing for a first access pointin a radio access network, the first access point being associated witha first cell of a number of cells within the radio access network, thefirst access point being adapted to connect at least one first userequipment being situated in the first cell, to a network infrastructure,comprising the steps of: receiving from the at least one first userequipment a report indicating whether a specific channel is used in asecond adjacent cell of said number of cells, the report being based ona first information sent from at least one second access pointassociated with the second adjacent cell, the first information beingdetected by the first user equipment and which information indicateswhether a specific channel is used or not in the second adjacent cell.

In accordance with the present invention, the object is also achieved bya method for a dynamic inter-cell channel sharing for a first userequipment in a radio access network, the radio access network comprisinga number of cells, the first user equipment being situated in a firstcell of said number of cells, the first user equipment is connectable toa network infrastructure via a first access point associated with thefirst cell, the method comprising the steps of: detecting if a firstinformation is sent from at least one second access point associatedwith a second cell of said number of cells, the second cell beingadjacent to the first cell, the first information indicating whether aspecific channel is used or not in the second adjacent cell, and sendinga report regarding whether the specific channel is used in the secondadjacent cell or not, to the first access point being situated in thesame first cell as the first user equipment, based on the detected firstinformation.

In accordance with the present invention, the object is also achieved byan arrangement for a dynamic inter-cell channel sharing in a firstaccess point in a radio access network, the first access point beingassociated with a first cell of a number of cells within the radioaccess network, the first access point being adapted to connect at leastone first user equipment being situated in the first cell, to a networkinfrastructure, the access point arrangement comprising means forreceiving from the at least one first user equipment a report indicatingwhether a specific channel is used in a second adjacent cell of saidnumber of cells, the report being based on a first information sent fromat least one second access point associated with the second adjacentcell, the information being detected by the user equipment and whichinformation indicating whether a specific channel is used or not in thesecond adjacent cell.

In accordance with the present invention, the object is also achieved byan arrangement for a dynamic inter-cell channel sharing in a first userequipment in a radio access network, the radio access network comprisinga number of cells, the first user equipment being situated in a firstcell of said number of cells, the first user equipment is connectable toa network infrastructure via a first access point associated with thefirst cell, the user equipment arrangement comprising: means fordetecting if a first information is sent from at least one second accesspoint associated with a second cell of said number of cells, the secondcell being adjacent to the first cell, the first information indicatingwhether a specific channel is used or not in the second adjacent celland means for sending a report regarding whether the specific channel isused in the second adjacent cell or not, to the first access point,based on the detected first information.

Since the first user equipment detects if the second access points inadjacent cells are using a specific channel and reports that to thefirst access point, and the first access point selects the specificchannel if it is not used in an adjacent cell according to the report,channels can be shared between cells dynamically, without simultaneousallocation of the same channel by more than one access point and withoutrequiring a central entity that coordinates the allocation.

An advantage of the present invention is that the radio channels betweenthe cells are shared dynamically depending on the current load in eachcell such that no inter-cell interference occurs. The inefficiencies ofa static allocation are avoided.

Another advantage of is that the scheme of the present invention doesnot require a central coordination entity or signalling communicationbetween the access points. Each access point can decide on channelassignment autonomously. Nevertheless, the efficiency of channel sharingcould be as good as with a central controller or with central schedulingentity.

Another advantage of the present invention is that the schedulingdecision remains in the access point, so all the advanced linkadaptation, frequency domain scheduling etc., mechanisms can be used.

Another advantage of the present invention is that the user equipmentsneed to perform only simple finding out if a channel is used byreference symbol sensing or broadcast channel reception and there is noneed to maintain signalling communication with neighbour access points.The user equipment does not necessarily have to do the detectingcontinuously but when required by the access point. The scheme accordingto he invention does not introduce additional measurement load on theuser equipment, since the user equipment anyway has to do similarreference symbol measurements for other reasons as well (e.g., channelestimation, link adaptation).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a radio access networkaccording to the present invention.

FIG. 2 is a diagram illustrating reference symbols according to thepresent invention.

FIG. 3 is a flow chart illustrating a method in an access pointaccording to the present invention.

FIG. 4 is a flow chart illustrating a method in an access point whenusing a channel on a packet-by-packet basis according to the presentinvention.

FIG. 5 is a block diagram illustrating an arrangement in an access pointaccording to the present invention.

FIG. 6 is a flow chart illustrating a method in a user equipmentaccording to the present invention.

FIG. 7 is a flow chart illustrating a method in a user equipment whenusing a channel on a packet-by-packet basis according to the presentinvention.

FIG. 8 is a block diagram illustrating an arrangement in a UserEquipment according to the present invention.

FIG. 9 is a block diagram illustrating a data carrier according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In cellular systems, frequency reuse is typically employed to avoidinter-cell interference. The frequency spectrum is divided into a numberof frequency bands, where each cell gets assigned a subset of theavailable bands. In a more general interpretation of frequency reuse theradio channel to be shared between cells can be a code in case of CodeDivision Multiple Access (CDMA) or a time-frequency grid (chunk) inOrthogonal Frequency Division Multiplexing (OFDM). The term channel willbe used to refer to such a piece of the radio channel in general.

FIG. 1 depicts a radio access network 100 comprising a number of cellsof which cells 112, 114 and 116 are depicted in FIG. 1, and which radioaccess network 100 uses technologies such as e.g. Code Division MultipleAccess (CDMA) or Orthogonal Frequency Division Multiplexing (OFDM).

The radio access network 100 further comprises, associated with each ofthe number of cells 112, 114 and 116, a respective access point 122, 124and 126. The access points are connectable to an infrastructure network130 such as e.g. the Public Switched Telephone Network (PSTN), an IPnetwork or a radio access network.

A number of user equipments A1, B1, C1, C2 are located under radiocoverage of the radio access network 100 and are connectable to theinfrastructure network 130, by means of the associated with the cell inwhich it is currently positioned. In the current scenario in FIG. 1, theuser equipment A1 in cell 112 is connectable to the infrastructurenetwork 130 via access point 122, the user equipment B1 in cell 114 isconnectable to the infrastructure network 130 via access point 124, theuser equipment C1 and C2 in cell 116 are connectable to theinfrastructure network 130 via access point 126. The user equipments maybe mobile terminals, personal digital assistants (PDA), laptop computersor any type of device capable of communicate radio resources.

When any access point in a cell (any of the access points in FIG. 1) isusing a specific channel, the access point sends out informationindicating that the specific channel is used, i.e. occupied. This may beperformed by defining signal symbols and send reference symbols on adown link channel or by sending out the information by using a broadcastchannel. These methods will be described more in detail below. Thisinformation, sent out by the access points in the radio access network100 is receivable by the user equipments in adjacent cells, i.e. cellsadjacent to the cell that is associated with the access point sendingthe information. The user equipments receiving this information reportthe information to the access point of the cells they are communicatingwith. This means that the access point receive information, from alluser equipments in its cell, whether a channel is occupied in adjacentcells and accordingly can refrain from using that channel and therebyavoid channel interference. This enables a dynamic inter-cell channelsharing. The access point may set from which channels it wants toreceive reports about by telling the user equipment the identities ofthe channels/reference symbols or set from which N adjacent accesspoints it wants reports about by telling the user equipment theidentities of the N adjacent access points.

Access Point

The invention will now be described as seen from a point of view of thefirst access point 122 in the first cell 112. The first access point 122requires starting of scheduling traffic on a specific channel andtherefore requires to know which channels that are available i.e.channels that are not used in adjacent cells. The first access point 122sends a request to the first user equipment A1 requesting a report. Thereport indicating whether the specific channel is used in a secondadjacent cell 114, 116 of said number of cells 112, 114, 116. The firstaccess point 122 receives, from the at least one first user equipmentA1, the report. The report is based on a first information sent from atleast one second access point 124, 126 associated with the secondadjacent cell 114, 116. The first information, that is to be detected bythe first user equipment A1, indicates whether the specific channel isused or not in the second adjacent cell 114, 116. When the first accesspoint 122 starts using the specific channel in the first cell 112, itsends a second information to be detected by a second user equipment B1,C1, C2 in a second cell 114, 116 being adjacent to the first cell 112.The second information indicates that the specific channel is used inthe first cell 112. The expressions first information and secondinformation is used in this example to distinguish information that isreported to the first access point about available channels from theinformation that the first access point 122 sends out itself that thefirst access point 122 uses a selected channel.

In one embodiment, the information is sent by defining a referencesymbol, e.g. a so called pilot. The reference symbol is a known signalpattern that is known by all user equipments in the system. In this casea reference symbol is associated with each of a respective uplink anddownlink channels of the specific channel. When a specific channel isused in the cell 112, see FIG. 1, the access point 122 keeps sending areference symbol that corresponds to that specific channel, also calledthe “busy reference symbol”.

For detecting the first information, the user equipments measure onreference symbols sent by adjacent access points. In the scenario inFIG. 1, user equipment B1 in adjacent cell 114 and user equipments C1and C2 in adjacent cell 116 measure on the busy reference symbol sent byaccess point 122. The user equipment B1 reports the reference symbol ithas heard to “its” access point 124, and user equipments C1 and C2 bothreport the reference symbol they have heard to their access point 126.Thereby, each access point knows which channels are used in the adjacentcells and they can start scheduling traffic on a channel that is notused in an adjacent cell i.e. avoid scheduling traffic on the samechannel, which would result in inter-cell interference.

In one embodiment, the first access point 122 does not start schedulingtraffic on the specific channel for a certain time frame, calleddetection window, which is allocated in order to detect any possiblecollision with another access point, in this example the second accesspoints 124, 126. That is, to detect when the second access points 124,126 allocates the same channel and activates the same reference symbolat the same time. In such a case the first user equipment A1 will detecteither a jammed reference symbol or if the access point identity can bedecoded from the reference symbol it will detect that two second accesspoints 124, 126 are sending the same reference symbol simultaneously.When the first user equipment A1 reports a collision to the first accesspoint 122, the first access point 122 will enter a backoff phase, duringwhich it stops sending the reference symbol and draws a random numberuntil it refrains from any further attempt to allocate that channel.This time frame is called the backoff window and the time is defined bythe random number. i.e. the backoff window is used by the first accesspoint 122 to resolve situations when more than one access point requiresusing to the same channel simultaneously. After the backoff window haselapsed and the first access point 122 detects that the channel isunused based on the first user equipment A1 reference symbol reports, itrepeats the same mechanism again i.e., evaluates first user equipment A1reference symbol report, selects an available channel, starts sendingcorresponding reference symbol, to acquire the channel. If the specificchannel is still used nothing happens, that is, this specific channelwill still be unavailable for the first access point 122, just as anyother channel could be unavailable as well. The first access point 122will continuously receive reports on all channels, so this specificchannel will be treated as any other channel. When it becomes free somelater point in time the first access point 122 may try to get it. Notealso that during the backoff window the first access point 122 can stilltry to acquire other channels, i.e., the backoff window only blocks theaccess to that particular channel. (This same mechanism is applicablealso for the case when the channel occupancy information is sent onbroadcast channels, see below.) The user equipments B1, C1, C2 in theadjacent cells 114, 116 will also detect the collision and will reportto the second access point 124, 126 (they each report to their ownaccess point), which second access point 124, 126 also will enter thebackoff phase. The backoff window may be increased after each successivecollision. If no collision of reference symbols is reported by the firstuser equipment A1 in the detection window, the first access point 122assumes that it has successfully acquired the selected channel and itstarts scheduling traffic on that channel. As mentioned above, the firstaccess point 122 keeps sending the reference symbol continuously inorder to indicate to adjacent second user equipments B1, C1, C2 that thecorresponding channel is in use. When the load decreases and the firstaccess point 122 no longer requires the selected channel the firstaccess point 122 stops sending the second information corresponding tothe selected channel, i.e. in this example the first access point 122stops sending the busy reference symbol corresponding to the selectedchannel and thereby the selected channel becomes available for possibleuse by adjacent second access points 124, 126.

Referring to FIG. 2 depicting uplink channels 200 and downlink channels201. Reference symbols for each channel both in uplink C_(u,i) anddownlink C_(d,j) a corresponding reference symbol channel is associated,denoted by P_(u,i) and P_(d,j), respectively. This means that uplinkchannel number 1 C_(u,1) corresponds to reference symbol P_(u,1) aspointed out by arrow 203, downlink channel number 1 C_(d,1) correspondsto reference symbol P_(d,1) pointed out by arrow 204, uplink channelnumber N C_(u,N) corresponds to reference symbol P_(u,N) as pointed outby arrow 205 and downlink channel number N C_(d,N) corresponds toreference symbol P_(d,N) pointed out by arrow 206, where N is the numberof channels.

When the specific channel is in use in cell 112, the access point 122keeps sending the corresponding reference symbol continuously, whichwill enable user equipment B1 in adjacent cell 114 and user equipmentsC1 and C2 in adjacent cell 116 to sense the reference symbol and reportto their own access points 124, 126, the channels that are in use in theadjacent cell as described above.

In one embodiment of the invention, an access point identity of thefirst access point 122 sending the reference symbol is encoded into thereference symbols, which enables the user equipments B1, C1, C2listening to the reference symbols to determine which access point 122that sends the reference symbol. Also the other access points 124 and126 have encoded their reference symbols in the same way. Then theaccess point 122 can set the identity of the reference symbols fromwhich adjacent access points 124, 126 it requires reports by. A requestto find the first information may comprise the identity of adjacentsecond access points 124, 126 from which the first user equipment A1shall detect if the first information is sent.

By associating a downlink reference symbol not only to downlink channelsbut also to uplink channels as depicted in FIG. 2, user equipments inadjacent cells can detect that in case they would use the correspondingchannels in the uplink, their transmission would interfere with theuplink transmissions of other user equipments in the adjacent cell.Without the user equipment reporting of the uplink channels used byadjacent cells, the access point would be unable to detect that theuplink transmission of its own user equipment would interfere withtransmissions in adjacent cells.

The use of downlink reference symbols associated with downlink channelsis being employed in prior art solutions, but these reference symbolsare used for other reasons, such as for synchronization, for channelestimation/demodulation or for link adaptation and for frequency domainscheduling such as channel quality indicator (CQI) reporting. Accordingto the present invention, in these cases where downlink referencesymbols already are used but for other reasons, additional specificdownlink reference symbols that are used for indicating the occupancy ofthe corresponding downlink channels, are defined as shown in FIG. 2.Thus, these reference symbols will be separate from the referencesymbols that are used for the other reasons e.g. CQI measurements.

In an alternative embodiment of present invention, the access point 122can use the broadcast channel to broadcast the second information ofwhether an uplink and downlink channel is used or not, as an alternativeto defining reference symbols. The broadcast information may comprise ofset of vectors containing channel identities φ for uplink channels(UL_ch_IDs) and channel identities θ for down link channels (DL_ch_IDs)that are in-use channel (DL_ch_use) as expressed in (1)-(2). i.e. thevector includes the identities of the currently occupied channels andthere is one such vector for uplink and downlink channels.UL_ch_IDs=[φ₁,φ₂, . . . , φ_(k)]  (1)DL_ch_IDs=[θ₁,θ₂, . . . , θ_(L)]  (2)

Where UL_ch_IDs indicates identities of uplink channels, and φ₁ is theidentity of first channel, φ₂ the identity of the second channel andφ_(k) is the identity of channel number K and where DL_ch_IDs indicatesidentities of downlink channels, and θ₁, is the identity of the firstchannel θ₂ is the identity of the second channel and θ_(L) is theidentity of channel number L. In the above expression it is assumed thechannel occupancy of only K out of N total channels in the uplink andonly L out of M total channels in the downlink broadcast.

The user equipments B1, C1, C2 in the adjacent cells 114 and 116 readthe broadcast channels of the adjacent access point 122 and report thechannel occupancy information back to their own access points 124, 126.

The detection window and the backoff window mechanisms that aredescribed above are applicable also in this alternative embodiment.

The method steps performed by the first access point 122 according tothe present invention will now be described with reference to the flowchart in FIG. 3.

-   301. The first access point 122 sends a request to the at least one    first user equipment A1 to send a report comprising a first    information indicating whether a specific channel is used in a    second adjacent cell 114, 116.-   302. The first access point receives and evaluates the report from    the at least one first user equipment A1 and selects the specific    channel if available to be used, based on the evaluated first    information.-   303. The first access point 122 sends out a second information,    indicating that the channel is used, by sending busy reference    symbols or related broadcast information associated with the    selected channel. The second information may be detected by second    user equipments B1, C1, C2 in second cells 114, 116 being adjacent    to the first cell 112, which each respective second user equipment    B1, C1, C2 report the second information in its second cell to its    respective associated second access point 124, 126.-   304. The first access point 122 keeps on receiving and evaluating    first information reports from the first user equipment A1 during a    detection window. The first access point 122 does not start to    schedule traffic on the selected channel for a certain time frame,    the so-called detection window, which is allocated in order to    detect any possible collision with another access point. That is in    order to detect whether another adjacent access point, i.e. in this    example the second access points 124, 126 allocates the same    specific channel and activates the same reference symbol or sends    the related information at the same time as the first access point    122.-   305. Has any of the at least one user equipment A1 reported that the    specific channel is used in a second adjacent cell 114, 116?-   306. If answer is no for the question in method step 306, the second    access point 122 starts to schedule traffic on the selected specific    channel.-   307. When the first access point 122 no longer requires the selected    channel it releases the specific channel and stops sending out the    second information, indicating that the channel is used, by stopping    sending busy reference symbols or related broadcast information    associated with the selected channel. Thereby the selected channel    is available for possible use by other access points, i.e. in this    example the second access points 124, 126.-   308. If answer is yes for the question in method step 305, the first    access point 122 stops sending out the second information using busy    reference symbols or related broadcast information associated with    the selected channel.-   309. The first access point 122 draws a random number until it    refrains from any further attempt to allocate the selected channel.    This time frame is called the backoff window. The first access point    122 keeps receiving and evaluating first information reports from    the first user equipment A1 during the back off window. During the    backoff window the first access point is only banned from reserving    the selected channel but it can still reserve other available    channels. The first access point 122 evaluates the reports and it    may select another channel or when the backoff window expires and    the channel is available, it can try again to reserve the selected    channel by sending out a second information, indicating that the    channel is used, by sending busy reference symbols or related    broadcast information associated with the selected channel, while it    keeps listening for first user equipment A1 reports during the    detection window time, i.e., the same procedure over again from    method step 302.

In a second embodiment, the same mechanism is used to share theavailable channels between cells on a packet-by-packet basis. This meansthat an access point reserves a channel only for the time needed to senda packet. Such a scheme may be most convenient in the uplink where theuser equipment has to send a channel request to its access point anywaybefore it can start transmission. Therefore a report comprising theinformation detected by the user equipment is preferably comprised in achannel request sent to its access point. This enables the access pointto select a channel that is not used in adjacent cells, to be assignedfor the uplink transmission of the user equipment, which is signalledback to the user equipment in a channel grant message. The method stepsperformed by the first access point 122 according to the secondembodiment of the present invention will now be described with referenceto the flow chart in FIG. 4.

-   401. An uplink scheduling request is received from a first user    equipment A1, the request comprises a report, which report comprises    a first information indicating whether a specific channel is used in    a second adjacent cell 114, 116.-   402. The first access point 122 evaluates the reported first    information included in the request. Based on the report, the first    access point 122 selects an available channel that is not used in    the second adjacent cell 114, 116, to be assigned to the first user    equipment A1. The first access point 122 then creates a scheduling    grant according to the selected channel.-   403. The first access point 122 starts sending out a second    information indicating the selected channel is used by sending out    the busy reference symbol corresponding to the selected uplink    channel or related broadcast information associated with the    selected channel. The second information may be detected by second    user equipments B1, C1, C2 in second cells 114, 116 being adjacent    to the first cell 112.-   404. The first access point 122 sends a scheduling grant to the    first user equipment A1-   405. The first access point 122 receives uplink transmission from    the user equipment A1.-   406. When the scheduling grant expires the first access point 122    releases the selected channel by stop sending the busy reference    symbols or related broadcast information.

To perform the method steps, the first access point 122 comprises anarrangement 500 as depicted in FIG. 5. The access point arrangement 500comprises means for sending 501 a request to the at least one first userequipment A1 in the first cell 112, requesting to find the firstinformation and means for receiving 502 from the at least one first userequipment A1 a report indicating whether a specific channel is used in asecond adjacent cell 114, 116 of said number of cells 112, 114, 116, thereport being based on the first information sent from at least onesecond access point 124, 126 associated with the second adjacent cell114, 116, the information being detected by the user equipment A1 andwhich information indicating whether a specific channel is used or notin the second adjacent cell 114, 116.

The access point arrangement 500 further comprises means for sending 503a second information when using the specific channel in the first cell112, the second information to be detected by a second user equipmentB1, C1, C2 in the second cell 114, 116 being adjacent to the first cell112, the second information indicating that the specific channel is usedin the first cell 112.

The access point arrangement 500 further comprises means for evaluating504 the first information in the report, means for selecting 505 thespecific channel to be used, if the specific channel is availableaccording to the evaluation, and means for scheduling traffic 506 on theselected specific channel. It further comprises means for stopping 507to send the second information when the specific channel is not requiredfor use any more and also means for stopping 508 to send out the secondinformation if receiving a report indicating that the specific channelis used in a second adjacent cell 114, 116 during detection window.

In one embodiment the sending means 502 includes means for sending 509 areference symbol P_(u,i), P_(d,j) corresponding to the used specificchannel. In that case the arrangement 500 comprises means 510 forassociating a reference symbol P_(u,i), P_(d,j) with each of arespective uplink C_(u,i) and downlink C_(d,j) channels of the specificchannel. In another embodiment there is also a means 511 for encoding anaccess point identity, of the first access point 122 sending thereference symbol, into the reference symbols P_(u,i), P_(d,j). Theaccess point arrangement 500 may also comprise means 512 for comprisingthe identity of adjacent second access points 124, 126 from which thefirst user equipment (A1) shall detect if the first information is sentinto the request to find the first information.

In another embodiment the sending means 502 includes means 513 forsending the second information the broadcast channel which secondinformation may comprise a set of vectors containing channel identityand corresponding channel occupancy.

The access point arrangement 500 further comprises a processor 514 whichtogether with computer program code performs the functions of theinvention.

User Equipment

In accordance with the present invention and seen from a general pointof view of a first user equipment A1 in a first cell 112 will now bedescribed. As described above, the first access point requires to startscheduling traffic on a specific channel and therefore requires to knowwhich channels that are available i.e. channels that are not used inadjacent cells. The first user equipment A1 detects if a firstinformation is sent from at least one second access point 124, 126associated with a second cell 114, 116 being adjacent to the first cell112. The first information indicates whether the specific channel isbeing used or not in the second adjacent cell 114, 116. The first userequipment A1 then reports to the first access point 112 whether thespecific channel is used in the second adjacent cell 114, 116 or not,based on the detected first information. The first access point 112 issituated in the same first cell 112 as the first user equipment A1.

The second access point 124, 126 may send the first information bydefining reference symbols or using the broadcast channel as describedabove. Therefore, the detecting of the first information may beperformed by measurement on reference signals such as reference symbolsthat the second access point 124, 126 sends on the downlink channel.Whether a channel is occupied or not can be through the reference symbolbeing above or below a threshold value, set by the first access point122. Another way is for the user equipment A1 to listen to the broadcastchannel if the second access point 124, 126 sends the information thatway.

In one embodiment, the user equipment A1 receives a request from thefirst access point 122, where the request comprises the identities ofthe channels/reference symbols about which the first access point 122requires reports. In another embodiment, the user equipment A1 receivesa request from the first access point 122, where the request comprisesthe identities of the adjacent access points 124, 126 from which thefirst access point 122 requires reports.

In one embodiment of the invention, an access point identity of therespective adjacent access points 124, 126 sending the reference symbolis encoded into reference symbols, in that case the user equipment A1listens to the reference symbols to determine which adjacent accesspoints 124, 126 that sends the reference symbols. The user equipment A1then reports the identity of the respective adjacent access points 124,126 together with the information whether the channel is occupied or notso that the first access point 122 knows in which cell a certain channelis used. In another embodiment of the present invention, also thequality of reference symbols listened to is added to the report. Thiscould allow the first access point 122 to make more sophisticateddecisions by comparing the actual measured signal quality by individualuser equipments. i.e. when the first user equipment A1 sends a reportwithout quality information it is only a binary information (yes or no)but when the actual quality is also reported it is more information andthe first access point 122 may compare the qualities from different userequipments that have reported.

In a further embodiment, the user equipment A1 reports identity andquality of reference symbols of all N adjacent access points 124, 126 toits own access point, where N e.g. is set by the radio access network100 or the first access point. Then the access point 122 decides whichone to use or not. To limit the information sent in this case, the userequipment reports identities of channels of the reference symbol qualityof which is below a threshold value (gamma), where gamma may be set bythe radio access network 100 or the first access point A1

In one scenario, more than one second access points 124, 126 is sendingthe same reference symbol In that case the first user equipment A1detects either a jammed reference symbol, if the signal strength fromthe two or more second access points 124, 126 are approximately the sameat the user equipment A1, or it can detect the reference symbolcorrectly if there is one strong reference symbol in the detected signalat the location of the user equipment A1. This implies that at leastthree states of a reference symbol: detected, not detected or jammed maybe reported by the user equipment A1.

The method steps performed by the first user equipment 122 according tothe present invention will now be described referring to the flow chartin FIG. 6.

-   601. The first user equipment A1 receives a request from the first    access point 122 requesting whether a first information is sent from    at least one second access point 124, 126 associated with a second    cell 114, 116 being adjacent to the first cell 112, where the first    information indicates whether a specific channel is being used or    not in the second adjacent cell 114, 116.-   602. The first user equipment A1 starts to detect if the first    information is sent by measuring on busy reference symbols    corresponding to the specific channel or read broadcast information    related to the specific channel that is sent by the second access    point 124, 126.-   603. When performed the detecting step, the first user equipment A1    sends a report comprising the first information to the first access    point 122 periodically or when solicited, when there is a change in    the sensed reference symbols or until the first to access point 122    requests to stop.

In the second embodiment mentioned above, the method of the presentinvention is used to share available channels between cells on apacket-by-packet basis as mentioned above under the access point. Themethod steps performed by the first user equipment A1 according to thesecond embodiment of the present invention will now be described withreference to the flow chart in FIG. 7.

-   701. Prior to initiating uplink transmission, the user equipment A1    detects if a first information is sent from at least one second    access point 124, 126 associated with a second cell 114, 116 being    adjacent to the first cell 112, the first information indicates    whether a specific channel is being used or not in the second    adjacent cell 114, 116. The first user equipment A1 finds the first    information by measuring on busy reference symbols corresponding to    the specific channel or listening to broadcast information related    to the specific channel that is sent by the second access point 124,    126.-   702. The first user equipment A1 sends a scheduling request and a    report comprising the detected first information to the first access    point 122.-   703. The user equipment A1 keeps detecting if first information is    sent by the second access point 124, 126 by keeping on measuring on    busy reference symbols corresponding to the specific channel or    keeping on reading broadcast information related to the specific    channel.-   704. The user equipment A1 receives a scheduling grant for a    channel, selected by the first access point 122 based on the    reported first information as a response to the request from the    first access point 122.-   705. Is the selected channel still free? The answer will be based on    whether any no reference symbols have been measured or any    conflicting broadcast information have been detected during method    step 703 when the first user equipment A1 keeps on detecting the    first information? If the channel is no longer free, the method goes    back to step 702 by sending a new scheduling request and the latest    detected first information.-   706. If the selected channel is still free the user equipment A1    sends uplink traffic according to the scheduling grant.

To perform the method steps according to the present invention, thefirst user equipment A1 comprises an arrangement 800 as depicted in FIG.8. The user equipment arrangement 800 comprises means for detecting 801if the first information is sent from at least one second access point124, 126 associated with the second cell 114, 116 of said number ofcells 112, 114, 116, the second cell 114, 116 being adjacent to thefirst cell 112, the first information indicating whether a specificchannel is used or not in the second adjacent cell 114, 116 and meansfor reporting 802 whether the specific channel is used in the secondadjacent cell 114, 116 or not, to the first access point 122 beingsituated in the same first cell as the first user equipment A1, based onthe detected first information. The reporting means 802 may includemeans for comprising an access point identity, of the second accesspoint 124, 126 that has sent the first information into a reportreported by the reporting means 802.

In one embodiment the detecting means 801 includes means 803 formeasuring if a reference symbol P_(u,i), P_(d,j) is sent from the secondaccess point 122.

In another embodiment the detecting means 801 includes means 804 forlistening to a broadcast channel if a first information is sent from thesecond access point 122.

A further embodiment comprises means for receiving 805 a request fromthe first access point 122 requesting whether the first information issent from the second access point 124, 126. Then the detecting processis performed when the request is received.

In one embodiment the channels are using a packet-by-packet basis, inthis case the user equipment arrangement 800 further comprises means forsending 806 a scheduling request to the first access point 122comprising the report of whether the specific channel is used in thesecond adjacent cell 114, 116 or not, the user equipment arrangement 800may also comprise means for receiving 807 a scheduling grant for thespecific channel, selected by the first access point 122 based on thereported first information.

The user equipment arrangement 800 further comprises a processor 809which together with computer program code performs the functions of theinvention.

The dynamic inter-cell channel sharing methods according to the presentinvention can be implemented through one or more processors, such as theprocessor 514 in the access point arrangement depicted in FIG. 5 and theprocessor 809 in the user equipment arrangement depicted in FIG. 8,together with computer program code for performing the functions of theinvention. The program code mentioned above may also be provided as acomputer program product, for instance in the form of a data carriercarrying computer program code for performing the method according tothe present invention when being loaded into the access point and/or theuser equipment. One such carrier 900, in the form of a CD ROM disc isgenerally outlined in FIG. 9. It is however feasible with other datacarriers such as a memory stick. The computer program code canfurthermore be provided as pure program code on a server and downloadedto the access point and/or user equipment remotely.

The present invention is not limited to the above-describe preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending claims.

1. A method for dynamic inter-cell channel sharing for a first accesspoint in a radio access network, the first access point being associatedwith a first cell of a number of cells within the radio access network,the first access point being adapted to connect a first user equipmentbeing situated in the first cell to a network infrastructure, the methodcomprising the steps of: receiving from the first user equipment, areport indicating whether a specific channel is being used in a secondcell adjacent to the first cell, the report being based on a firstinformation sent from a second access point associated with the secondadjacent cell, the first information being detected by the first userequipment and indicating whether a specific channel is used or not inthe second adjacent cell; selecting the specific channel for use in thefirst cell only when the information indicates the specific channel isnot being used in the second cell; when using the specific channel inthe first cell, sending a second information indicating that thespecific channel is being used in the first cell; continuing to receiveand evaluate first information reports from the first user equipmentduring a detection window in order to detect whether the second accesspoint allocates the same specific channel; upon receiving a reportindicating that the specific channel is used in the second cell duringthe detection window, stop sending the second information; andcontinuing to receive and evaluate reports from the first user equipmentduring a backoff window defined by drawing a random number untilrefraining from any further attempt to allocate the selected specificchannel.
 2. The method according to claim 1, comprising the further stepof: sending a request to the first user equipment requesting the report.3. The method according to claim 2, wherein the request includes theidentity of the second access point.
 4. The method according to claim 1,further comprising the steps of: evaluating the report; and selectingthe specific channel to be used when the specific channel is availableaccording to the evaluation.
 5. The method according to claim 1, furthercomprising the step of: when the specific channel is no longer requiredfor use in the first cell, stop sending the second information.
 6. Themethod according to claim 1, wherein the inter-cell channel sharing isused for channels between cells on a packet-by-packet basis, and themethod further comprises the step of: receiving the first informationreport in an uplink scheduling request from the first user equipment. 7.The method according to claim 1, wherein the step of sending a secondinformation is performed by sending a reference symbol (P_(u,i,)P_(d,j)) corresponding to the used specific channel.
 8. The methodaccording to claim 7, wherein a reference symbol (P_(u,i), P_(d,j) isassociated with each of a respective uplink (C_(u,i)) and downlink(C_(d,j)) channels of the specific channel.
 9. The method according toclaim 7, wherein an access point identity of the first access pointsending the reference symbol is encoded into the reference symbols(P_(u,i), P_(d,j)).
 10. The method according to claim 2, wherein therequest to the first user equipment requesting the report includes theidentity of adjacent second access points from which the first userequipment shall detect if the first information is sent.
 11. The methodaccording to claim 1, wherein the second information is sent on abroadcast channel.
 12. The method according to claim 11, wherein thesecond information includes a set of vectors containing channel identityand corresponding channel occupancy.
 13. A computer program productstored on a non-transitory memory in a first access point associatedwith a first cell in a radio access network, the computer programproduct comprising computer program code for causing a processor in thefirst access point to control the access point to execute the steps of:receiving from a user equipment, a report indicating whether a specificchannel is used in a second cell adjacent to the first cell in the radioaccess network, the report being based on information sent from a secondaccess point associated with the second adjacent cell, the informationbeing detected by the first user equipment and indicating whether aspecific channel is used or not in the second cell; selecting thespecific channel for use in the first cell only when the informationindicates the specific channel is not being used in the second cell;when using the specific channel in the first cell, sending a secondinformation indicating that the specific channel is being used in thefirst cell; continuing to receive and evaluate first information reportsfrom the first user equipment during a detection window in order todetect whether the second access point allocates the same specificchannel; upon receiving a report indicating that the specific channel isused in the second cell during the detection window, stop sending thesecond information; and continuing to receive and evaluate reports fromthe first user equipment during a backoff window defined by drawing arandom number until refraining from any further attempt to allocate theselected specific channel.
 14. An arrangement in a first access pointfor dynamic inter-cell channel sharing in a radio access network, thefirst access point being associated with a first cell of a number ofcells within the radio access network, the first access point beingadapted to connect a first user equipment being situated in the firstcell to a network infrastructure, wherein the access point arrangementis configured to: receive from the first user equipment, a reportindicating whether a specific channel is used in a second cell adjacentto the first cell, the report being based on a first information sentfrom a second access point associated with the second adjacent cell, thefirst information being detected by the user equipment and indicatingwhether a specific channel is used or not in the second cell; select thespecific channel for use in the first cell only when the informationindicates the specific channel is not being used in the second cell; andsend a second information when using the specific channel in the firstcell, the second information to be detected by a second user equipmentin the second cell being adjacent to the first cell, the secondinformation indicating that the specific channel is used in the firstcell, wherein the access point arrangement is configured to send areference symbol (P_(u,i), P_(d,j)) corresponding to the used specificchannel.
 15. The access point arrangement according to claim 14, whereinthe access point arrangement is further configured to: send a request tothe first user equipment in the first cell, requesting the first userequipment to find the first information.
 16. The access pointarrangement according to claim 14, wherein the access point arrangementis further configured to schedule traffic on the selected specificchannel.
 17. The access point arrangement according to claim 14, whereinthe access point arrangement is further configured to stop sending thesecond information when the specific channel is no longer required foruse in the first cell.
 18. The access point arrangement according toclaim 14, wherein the access point arrangement is further configured tostop sending the second information if the arrangement receives a reportindicating that the specific channel is used in the second cell during adetection window.
 19. The access point arrangement according to claim14, wherein the inter-cell channel sharing is used for channels betweencells on a packet-by-packet basis, wherein the first information reportis receivable in an uplink scheduling request from the first userequipment.
 20. The access point arrangement according to claim 14,wherein the access point arrangement is further configured to associatea reference symbol (P_(u,i), P_(d,j)) with each of a respective uplink(C_(u,i)) and downlink (C_(d,j)) channels of the specific channel. 21.The access point arrangement according to claim 14, wherein the accesspoint arrangement is further configured to encode an access pointidentity, of the first access point sending the reference symbol, intothe reference symbols (P_(u,i), P_(d,j)).
 22. The access pointarrangement according to claim 14, wherein the access point arrangementis configured to send the second information on the broadcast channel.23. The access point arrangement according to claim 22, wherein thesecond information comprises a set of vectors containing channelidentity and corresponding channel occupancy.
 24. An arrangement in afirst user equipment for dynamic inter-cell channel sharing in a radioaccess network, the radio access network comprising a number of cells,the first user equipment being situated in a first cell of said numberof cells, wherein the first user equipment is connectable to a networkinfrastructure via a first access point associated with the first cell,wherein the user equipment arrangement is configured to: detect whethera first information is sent from a second access point associated with asecond cell of said number of cells, the second cell being adjacent tothe first cell, the first information indicating whether a specificchannel is used or not in the second adjacent cell, wherein the userequipment arrangement is configured to determine whether a referencesymbol (P_(U,i), P_(d,j)) is sent from the second access point; and senda report regarding whether the specific channel is used in the secondadjacent cell or not, to the first access point, based on the detectedfirst information.
 25. The user equipment arrangement according to claim24, wherein the user equipment arrangement is configured to include anaccess point identity of the second access point in the report.
 26. Theuser equipment arrangement according to claim 24, wherein the userequipment arrangement is configured to listen to a broadcast channel ifa first information is sent from the second access point.
 27. The userequipment arrangement according to claim 24, wherein the user equipmentarrangement is configured to receive a request from the first accesspoint requesting whether the first information is sent from the secondaccess point.
 28. The user equipment arrangement according to claim 24,wherein the inter-cell channel sharing is usable for channels betweencells on a packet-by-packet basis, and the user equipment arrangement isfurther configured to send a scheduling request to the first accesspoint including the report of whether the specific channel is used inthe second adjacent cell or not.
 29. The user equipment arrangementaccording to claim 24, wherein the user equipment arrangement isconfigured to receive a scheduling grant for the specific channel,selected by the first access point based on the reported firstinformation.